#include <iostream>
using namespace std;

typedef long long LL;

const int N = 25;

int n, m, a, b;
LL dp[N][N];

bool check(int i, int j)
{
	return (i == a && j == b) || (a != i && b != j && (abs(a - i) + abs(b - j) == 3));
}

int main()
{
	cin >> n >> m >> a >> b;

	n++; m++; a++; b++;

	// 初始化
	dp[0][1] = 1;

	for (int i = 1; i <= n; i++)
	{
		for (int j = 1; j <= m; j++)
		{
			if (check(i, j)) continue;

			dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
		}
	}

	cout << dp[n][m] << endl;

	return 0;
}